1. Field of Invention
This invention pertains to the field of aeronautics and describes a method of aircraft control for pilotless aircraft (Class 244, Subclass 190). The invention is a method of control that is applicable to fixed-wing airplanes, as well as to ornithopter type aircraft (those propelled by flapping wings).
2. Prior Art
Recently, by avoiding the use of expensive hobby servos, toy manufacturers have been able to produce radio-controlled airplanes inexpensively. One cost-saving approach is a twin motor design, marketed by Planrite Trading Company Ltd., 1105 8th Street East, Saskatoon, Saskatchewan, S7H 0S3, Canada, under the name “Sky Buddy”, in which directional control is achieved by varying the power to the left and right motors. Another technique is the use of simple magnetic actuators, rather than servos, to move control surfaces. This method has been used by Estes-Cox Corporation, 1295 H Street, Penrose, CO 81240 in their “Sky Rangers” toy planes. Both methods reduce the complexity and cost compared with hobby servo control systems. However, both methods do require additional control components (a second motor and associated control circuit, or the magnetic actuator).
Jasman Toys, 445 Marine View Ave., Suite 295, Del Mar, Calif. 92014, is producing a toy airplane called the “VrRoom Zoom” with no additional actuator. The control system consists of a radio receiver, an on/off motor control, and an electric motor, which propels the aircraft. The torque force produced by the motor causes the plane to fly in a circle when the motor is on. The plane flies straight when the motor is off Thereby, some degree of flight control is possible. This system has the desired level of simplicity, but it provides severely limited control.
For flapping wing aircraft, called ornithopters, none of the prior art control methods is suitable for an inexpensive toy. The twin motor approach is not applicable to ornithopters, and magnetic actuators do not exert enough force to be very effective in flapping flight. The on/off motor control system used by Jasman would not work well in an ornithopter, because ornithopters generally do not glide well. Therefore, remotely controlled ornithopters still rely on control surfaces moved by servos. They presently cost about ten times more than the least expensive remotely controlled airplanes.
U.S. Pat. No. 6,550,716 assigned to Neuros Co., Ltd, describes the control system commonly used in current radio controlled ornithopters. U.S. Patent Application #20020173217 by Andrew Sean Kinkade describes a similar system. In each case, the aircraft has a tail controlled by two servos. The radio receiver on board the ornithopter controls the two servos and an electronic speed control, which determines the speed of wing flapping. This system provides an effective means of flight control but it is too expensive to be used in a mass-market toy.
Ornithopter wing flapping mechanisms are normally designed to flap the wings symmetrically. It is considered undesirable to have an imbalance of the right and left wings, which would interfere with the action of the tail or other control surfaces. For example, Eric Edward Tomas (U.S. Pat. No. 6,544,092) and Desmond Leigh-Hunt (U.S. Pat. No. 4,155,195) used a double crank to flap the wings in a symmetrical fashion. However, some degree of asymmetry is often allowed, simply because eliminating it would require a more complex mechanism. U.S. Pat. No. 2,859,553 (P. H. Spencer), 3,626,555 (P. Albertini et al.), and US. Pat. No. 6,632,119 (Chernek, et al) show mechanisms that allow a degree of asymmetry. In these cases, however, the asymmetric flapping of the wings does not serve any purpose.